First, second TAP address control inputs for TAP TMS input
The disclosure describes a novel method and apparatus for making device TAPs addressable to allow device TAPs to be accessed in a parallel arrangement without the need for having a unique TMS signal for each device TAP in the arrangement. According to the disclosure, device TAPs are addressed by inputting an address on the TDI input of devices on the falling edge of TCK. An address circuit within the device is associated with the device's TAP and responds to the address input to either enable or disable access of the device's TAP.
1. An integrated circuit comprising:
A. a test data input lead, a test clock lead, a test mode select lead, and a test data output lead;
B. test access port circuitry including:
i. a TAP state machine having a test clock input connected to the test clock lead, a test mode select input, and control outputs;
ii. an instruction register having a test data input connected to the test data in lead, a test data output, control inputs connected to the control outputs, and instruction outputs;
iii. a data register having a test data input connected to the test data in lead, a test data output, and control inputs connected to the control outputs;
iv. multiplexer circuitry coupling the test data outputs of the instruction register and the data register to the test data out lead; and
v. control circuitry having an input connected to the test mode select lead, a first TAP control input, a second TAP control input, and an output connected to the test mode select input of the state machine; and
C. device address port circuitry having a test clock input coupled to the test clock lead, a test mode select input connected to the test mode select lead, a test data input connected to the test data input lead, a first TAP control output connected to the first TAP control input, and a second TAP control output connected to the second TAP control input.
2. The integrated circuit of claim 1 in which the state machine implements the states of Test Logic Reset, Run Test/Idle, Select-DR, Capture-DR, Shift-DR, Exit 1 -DR, Pause-DR, Exit 2 -DR, and Update-DR.
3. The integrated circuit of claim 1 in which the state machine implements the states of Test Logic Reset, Run Test/Idle, Select-DR, Capture-DR, Shift-DR, Exit 1 -DR, Pause-DR, Exit 2 -DR, and Update-DR in response to rising edges of a clock signal on the test clock lead and in response to a logic state on the test mode select lead.
4. The integrated circuit of claim 1 in which the test access port circuitry responds to data signals on the test data input lead in response to rising edges of a clock signal on the test clock lead and in response to a logic state on the test mode select lead.
5. The integrated circuit of claim 1 in which the first TAP control output is a global TAP control output.
6. The integrated circuit of claim 1 in which the second TAP control output is a group TAP control output.